Control system for drying apparatus



Dec. 29 1925- 1,567,710

- E. J. CARROLL CONTROL SYSTEM FOR DRYINGAPPARATUS Filed June 50, 1922 5 Sheets Sheet 1 1 jlqi. [Ll-j} @Lynv "E N TOR y Avai A TTO/(NE Y5 Dec. 29, 1925- 1,567,710

E. J. CARROLL CONTROL SYSTEM FOR DRYING APPARATUS Filed June 50, 1922 5 Sheeis-Sheet 2 41 %7MWW A TTORNE Vs Dec. 29 1925. 1,567,710

E. J. CARROLL CONTROL SYSTEM FOR DRYING APPARATUS Filed June 30, 1922 3 Sheets-Sheet 5 I 752v TOR pm WW Patented Dec. 29 1 925. I

UNITED. STATES 1,567,710 PATENT OFFICE.

EH11 J. CARROLL, OF CINCINNATI, OHIO, ASSIGNOR TO THE AMERICAN LAUNDRY MACHINERY COMPANY, OF CINCINNATI, OHIO, A CORPORATION OF OHIO.

CONTROL SYSTEM FOR DRYING APPARATUS.

Application filed June 30, 1922. Serial No. 571,885.

To all whom it may concern:

Be it known that I, EMIL J. CARROLL, a

citizen of the United States, residing at Cincinnati, in the county of- Hamilton and State of Ohio, have invented certam new and useful ImprovementsfinControl Systems for Drying Apparat of wh ch the following is a sp'e'cificatio I This invention relates'to a control system for drying apparatus and more particularly to a. system for controlling the operat1on of drying apparatus according-to the relative humidity of the air current flowmg therethrough.

The object of the invention 18 to provlde an improved control system which insures uniformly reliable drying results and automatically sto s the operation of the dry ng apparatus w en the materials being dried have reached such a dried condition as to bring air passing across the same to normal relative humidit thereby doing away with the necessity 0 opening the machine and feeling the material being dried or running the machine for a definite time interval, usually longer than that required.

Further objects of the invention are 1n part obvious and in part will appear more in detail hereinafter.

The invention comprises the construction and arrangement of parts hereinafter described and claimed.

In the drawings, Fig. 1 is a rear elevation of one form of drying apparatus with down at the air outlet from the machine; Fig. 3 is a sectional elevation on the line 33, Fig. 1, the controlling instrument being shown for convenience in elevation; Fig. 4 is a front elevation of the controlling instrument, parts being broken away and in section'to expose interior construction; Fig. 5 is an inverted sectional plan view on the line 5-5, Fig. 4; and Fig. 6 is a diagrammatic view of the electrical circuits.

The invention may be applied to any form of apparatus for drying any material, but particularly to drying apparatus in which materials are dried by circulating over 'or around the same a current of heated air to absorb and carry away moisture. The

a machine in which abrics or clothing which have been washed or dry cleaned and extracted to remove the greater part of the moisture or cleaning fluid are subjected to the effect of a heated air current while being agitated in said air current for removing the balance of the moisture or cleaning fluid. The particular construction and arrangement of the drying tumbler is largely immaterial. Merely for purposes of illustration the drawings showa drying tumbler including a suitable hollow frame or casing by suitable gearing (not shown) to the shaft 6 of the drum 3.

7 represents a heating chamber in which 18 a suitable heating device, such as steam coils or plpes 8 around which heated air flows to the channel 9 through which it is delivered to the drying chamber 2 and caused to flow through the rotating drum therein. The heated air is circulated through thr heating and drying chambers by the effect of a fan or blower 10, the suction side of which is connected to chamber 2 and'the outlet from which communicates with a channel 11 having an outlet 12 to the atmosphere. Both the outer casing and the periphery of drum 3 are provlded with the usual doors 13 through the openings for which the materials are inserted into and removed from the drum.

Fan .10 is driven in any suitable manner,

such as b an electric motor 14, the shaft of which is connected by a belt 15 with the shaft 16 of the fan.

In the present system the operation of the drying tumbler and more particularly the operation of either or both of the two drivmg motors 4, 14 is controlled by a device sensitive to the relative humidity of the air current passing over or through the fabrics or clothing being dried. This instrument or controlling device is of psychrometric character and embodies the usual wet and dry bulb thermometers. The instrument itself is illustrated more particularly in Figs. 2, 4 and 5. It comprises a suitable base or frame 20 ada ted for attachment to the frame of the ing and from which rises a wall 21 of insulating material. The base is shown as attached to the wall of the air current channel 11 and carried by said base and extending through said wall are protecting tubes '22 and 23, the first containing a dry bulb thermometer 24 and the second a wet bulb thermometer 25, the latter having its bulb surrounded by wick 26"dipping into reservoir 27 for liquid,1 such as water, which can be poured into said reservoir through a filling cup 28. The protecting tubes 22, 23 are, of course, provided witlr openings 29 through which the air current circulates to the thermometer bulbs. The frame of the instrument also includes a wall 30 separated from wall 21 by a side wall 31. In the cavity between said two walls are rotatable switch arms 32, 33 each having its stub shaft 34 sup ported by a bracket 35 attached to one end of a Bourdon tube 36. the two Bourdon' tubes communicating by tubes 37 with the two thermometers. As a result each thermometer by variations in the temperature effective thereon turns its'correspon'ding switch arm in one direction or the other. I With each switch arm cooperates a yielding brush 38 by which current from the outside circuit is conducted to the switch arms. Each switch arm is provided at its free end with a contact 39 cooperatingwith a series of contacts, one for each arm. spaced around the arc of movement. as shown in Fig. 4. In the zone between the two sets of contacts 40 are two other sets of contacts 41. lying in straight rows each of the contacts of said rows beinn connected by a wire 42 with a contact 40. Circuits'are completed across contacts of the two rows 41 by a series of what may be called coupl na' sets or devices. to wit. two series of contacts 43 in parallel rows carried by an insulating plate 44 and coupled in pairs by wires 45. Plates 44 with its coupling sets is insertable into and removable from a recess in the front wall of the instrument and is held in place therein by a removable plate 46. With each controlline instrument there is provided a series of diti'erent plate 44 havin the contacts of its two rows coupled in different wavs or paired differentl to correspond to difi'erent percentages of relative humidity. as will appear. so that the instrument can be made to respond to anv desired percen age of relative humiditv by including within it the proper one of the set of plates 44. In this respect the instrument is similar to the instrument hown and described more fully in a copending application for psychrometer,

filed by myself and George W. Johnson June 14, 1922. Serial No. 568,240, to which referattached to'the wall of the air current outlet with its thermometer bulbs sensitive and exposed to the air current flowing from the machine the switch arms actuated by the two thermometer bulbs will always assume positions corresponding to the characteristics of the air current to which they are subjected. The switch arm of the dry bulb. thermometer will occupy a position corresponding tothe normal dry bulb tem- Eerature, while the switch arm of the wet ulb thermometer will occupy a position corresponding to the evaporation point at that bulb. With each position of switch arm 32'throughout the range of its set ot contacts 40 there may be a corresponding position of switch arm 33 on any one of its several contacts 40, but in each of the differentpositions of arm 33 the relative humidity will be different from that in any other position of said arm. In other words. relative humidity, which is actually the ratio of the percentage of moisture in the atmosphere under 'given conditions of temperature and pressure to the total amount of moisture that the atmosphere might possibly contain under those conditions of temperature and pressure, is usually determined by calculation from empirical tables which take into consideration the pressure and the readings of the wet and dry bulb thermometers. The present instrument is simplified by omitting consideration of variation in pressure, but takes into question variations in the wet and dry bulb thermometer readinsrs. Each pair of positions of the two switch arms corresponds to a definite percentage of relative humidity.

Let. us assume, for example. that in the instrument shown in the drawing, the several contacts 43 are cross coupled or paired by wires 45 to correspond to 30 per cent relative humidity. It is clear that if switch arm 32 stands at one of the. contacts 40 at the same time that switch arm 33 stands at the one of its contacts 40 which happens to be coupled to the other contact 40 by a wire 45 a through circuit is completed between the two switch arms This through circuit-may be completed through any one of the coupling wires 45 and therefore at various normal dry bulb temperatures or at various evaporation points.

Control of the drying tumbler bv' the psychrometer device described is effected by circuits such as shown in Fig. 6 in which the two motors 4 and 14 are conventionally illustrated in circuit with main switches 50, 51 and the usual starting boxes 52, 53. The field of each motor has included in series therewith a retaining coil 54, said retaining coils cooperating with armatures 55 to hold the starting levers in running position. shunted across each of the holding coils 54 is a cut out circuit 59, the two out out circuits being normally open but adapted to be closed by a relay or switch 56 actuated by the coil 57 in a circuit 58 which circuit includes leads to the brushes 38 of the instrument shown in Fig. 4. The effect of this arrangement is as follows:

Usually at the beginning of the day the drying tumbler is operated for a few minutes without any load to cause the two switch arms to take positions corresponding to the temperature and moisture conditions in the machine. The relative humidity is determined either by calculation or by inserting in succession the several plates 44 until one is found based u on the existing relative humidity, assume here to be 30 percent. This plate 44 is then left in the instrument. A batch of material to be dried is now-placed in the drying tumbler and both starting box levers are thrown over to start the motors, it being assumed that the heater is turned on so that the flowing air will be heated. Warm air is passed over the clothes so that almost immediately the relative humidity of the traveling air current increases. Switch arm 32 corresponding to the dry bulb thermometer moves over due to the increase 1n dry bulb temperature and switch arm %3, wh1ch corresponds to the wet bulb thermometer moves over due to the rise in the evaporatlon point. As a result the two switch arms do not occupy positions at opposlte ends of the same couphn wire 45 and the circuit through thecoil 57 is broken. Holding coils 54 are therefore fully effective and hold the starting levers in running position. The relative humidity, of course, rises to a maximum and as themoisture is carried away begins to drop until finall a percentageof relative humidity is reac ed corresponding to that of the particular plate 44 in the controller. When this percentage is reached a through circuit is completed across the switch arms 32, 33, coil 57 is deenergized and both of the holding coils 54 are promptly shortcircuited, whereupon the starting levers fly over to ofi position and both motors stop. When the motors stop the attendant is, of course, advised that the relative humidity in the machine has reached normal atmospheric condition and the clothes are ready to be removed.

The control system described is efiective without the necessity of stopping the machines at intervals to test the dampness of the material by feeling it or of adopting a custom of always running the drier for a iven length of time. It also insures uni- ?orm drying results because the clothes are alwa '5 brought to a definite dry condition.

at I claim is:

1. Drying apparatus provided with a receptacle in which the material to be dried is placed, means for conducting air through said receptacle to produce a drying operation therein, and means sensitive to the humidity of the air in the receptacle for terminating the drying operation.

2. Drying apparatus, comprising a casing provided with a rotary receptacle for the,

or conducting material to be dried, means air through said receptacle to produce a drying operation upon the material in said receptacle, and means sensitive to the humidity of the air in said receptacle for terminating the drying operation.

3. Drying apparatus, comprising a drying machine in which the materlal to be dried is placed, means for conducting drying air over the material to be dried, and means sensitive to the humidity of the air current for stopping the air conducting means when the relative humidity of the air current reaches a predetermined percentage.

4. Drying apparatus, comprising a drying machine in which the material to be dried 1s placed, power means for conducting drying air through said machine, and means sensitive to the humidity of the air current for stopping operation of said power means when the material is dried to a predeterminedD degree.

5. rying apparatus, com risin a d 'n tumbler including a hollow di um in which thg material to be dried is agitated, means for rotating said drum, and means sensitive to the humidity of the air in said machine for controlling the drum rotating means.

6. Drying apparatus, comprising a drying tumbler including a rotatlng cylinder in which the material to be dried is agitated,

means for rotating said cylinder, means for conducting air through said cylinder, and means sensitive to the humidity of the air in said machine for controlling the operation of said drum rotating and air conducting means.

7. Drying apparatus, comprising a (1 ing tumbler including a rotating drum in w ich the material to be dried is placed, an electric motor for rotating said drum, means for conducting a current of air through said drum, an electric motor for o erating said alr conducting means, means or maintainmg the two motor circuits in running condition, and means sensitive to the humidity of the air in said machine for controlling said maintaining means and arranged to open said motor circuits when the material is dried to a predetermined degree.

In testimony whereof I hereby aifix my signature.

EMIL J. CARROLL. 

